1. Field of the Invention
This invention relates to a target assembly for deformographic storage display tubes (DSDT) and in particular to a method for fabricating the target structure.
2. Description of the Prior Art
The DSDT operates on the principle of generating minute deformations in a deformable material by the establishment of an electrostatic force from charges deposited by a cathode ray beam. The deformations in the material are translated via a reflection layer into a visual image by projection of the deformations through a Schlieren optical system. The construction of the DSDT provides it with a temporally and spatially controllable image persistence capability.
Target assemblies for deformographic display tubes are described, for example, in U.S. Pat. Nos. 3,636,084, 3,676,588, 3,858,080 and 3,879,630 which are assigned to the common assignee herein; and publications such as "Deformographic Material" by R. M. Ross et al; "Deformographic Film with Barrier Layer in Target Assembly" by R. J. Wohl; and "Applying Reflective Conductive Coating to a Deformable Polymer" by L. R. Yetter appearing in the IBM Technical Disclosure Bulletin, Vol. 13, No. 10, March 1971, p. 2948; Vol. 15, No. 5, October 1972, p. 1677; and Vol. 16, No. 7, December 1973, pp. 2045-46, respectively.
In some prior art deformographic target assemblies, a silver or other reflective conductive member is affixed to a deformable member made of materials such as silicone, rubber, a suitable gel, a liquid crystal or the like. The deformable material is chosen from those having low vapor pressure, low modulus of elasticity, low damping, reasonably high resistance and high stability, so that the material will not deteriorate under electron beam bombardment. Electrons from electron guns impinge on a non-conductive substrate to establish electron charges thereon in a desired electron charge pattern. The thickness of the deformable membrane increases or decreases in accordance with the strength of the electrostatic field resulting from the electron charge pattern established on the substrate, thereby affecting the reflection characteristics of the surface. Such prior art DSDT type target structures inherently involve a limited deformation sensitivity and deformation depth capability, as well as producing line-to-line interference in the deformation patterns. Known attempts to improve the deformation action of deformable membranes involve rather complex structures and fabrication procedures wherein supporting rods made of glass or bundles of fibers are spaced apart throughout the deformation material structure and a light reflecting membrane or material is stretched or placed on top of the rods.